Oxygen is not only the most abundant element in the Earth's crust, but it also makes up about one-fifth of the Earth's atmosphere. When it comes to the entire universe and solar system, oxygen is understood to be the third most abundant element. Approximately 90% of the weight of the ocean, is due to the presence of oxygen. When it comes to the air we breathe, oxygen makes up approximately 20%, with nitrogen at approximately 80%. There are other traces of elements, but all of them combined only add up to approximately 1%.